
The synaptic interactions between excitatory stellate cells and inhibitory parvalbumin interneurons in layer 2 of the medial entorhinal cortex are spatially organized, with direct connections between nearby neurons and indirect coordination of inputs at larger spatial scales.


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Interactions between excitatory and inhibitory neurons are critical to computations in cortical circuits but their organization is difficult to assess with standard electrophysiological approaches. Within the medial entorhinal cortex, representation of location by grid and other spatial cells involves circuits in layer 2 in which excitatory stellate cells interact with each other via inhibitory parvalbumin expressing interneurons. Whether this connectivity is structured to support local circuit computations is unclear. Here, we introduce strategies to address the functional organization of excitatory-inhibitory interactions using crossed Cre- and Flp-driver lines to direct targeted presynaptic optogenetic activation and postsynaptic cell identification. We then use simultaneous patch-clamp recordings from postsynaptic neurons to assess their shared input from optically activated presynaptic populations. We find that extensive axonal projections support spatially organized connectivity between stellate cells and parvalbumin interneurons, such that direct connections are often, but not always, shared by nearby neurons, whereas multisynaptic interactions coordinate inputs to neurons with greater spatial separation. We suggest that direct excitatory-inhibitory synaptic interactions may operate at the scale of grid cell clusters, with local modules defined by excitatory-inhibitory connectivity, while indirect interactions may coordinate activity at the scale of grid cell modules.

### Competing Interest Statement

The authors have declared no competing interest.

Synaptic interactions between stellate cells and parvalbumin interneurons in layer 2 of the medial entorhinal cortex are organized at the scale of grid cell clusters

spatially-organized-synaptic-interactions-between-excitatory-stellate-cells-and-inhibitory-parvalbumin-interneurons-in-layer-2-of-the-medial-entorhinal-cortex


Spatially Organized Synaptic Interactions Between Excitatory Stellate Cells and Inhibitory Parvalbumin Interneurons in Layer 2 of the Medial Entorhinal Cortex
